Fix #51: Catching SIGSEGV not needed anymore

This patch fixes issue #51 by reverting b4b63d3, which is not needed
anymore since service callbacks have been removed from Finit3.

The `sig_unblock()` function, called for each forked off child, should
now be balanced with caught signals.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

service.c

@@ -185,7 +185,7 @@ static int service_start(svc_t *svc)
 	/* Declare we're waiting for svc to create its pidfile */
 	svc_starting(svc);
 
-	/* Block sigchild while forking.  */
+	/* Block SIGCHLD while forking.  */
 	sigemptyset(&nmask);
 	sigaddset(&nmask, SIGCHLD);
 	sigprocmask(SIG_BLOCK, &nmask, &omask);

sig.c

@@ -90,7 +90,7 @@ shutop_t halt = SHUT_DEFAULT;
 static int   stopped = 0;
 static uev_t sigterm_watcher, sigusr1_watcher, sigusr2_watcher;
 static uev_t sighup_watcher,  sigint_watcher,  sigpwr_watcher;
-static uev_t sigchld_watcher, sigsegv_watcher;
+static uev_t sigchld_watcher;
 static uev_t sigstop_watcher, sigtstp_watcher, sigcont_watcher;
 
 void mdadm_wait(void);
@@ -281,15 +281,6 @@ static void sigchld_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
 	} while (pid > 0);
 }
 
-/*
- * SIGSEGV: mostly if service callbacks segfault
- */
-static void sigsegv_cb(uev_t *UNUSED(w), void *UNUSED(arg), int UNUSED(events))
-{
-	_e("PID %d caused a segfault!\n", getpid());
-	exit(-1);
-}
-
 /*
  * SIGSTOP/SIGTSTP: Paused by user or netflash
  */
@@ -393,9 +384,6 @@ void sig_setup(uev_ctx_t *ctx)
 	/* After initial bootstrap of Finit we call the service monitor to reap children */
 	uev_signal_init(ctx, &sigchld_watcher, sigchld_cb, NULL, SIGCHLD);
 
-	/* Trap SIGSEGV in case service callbacks crash */
-	uev_signal_init(ctx, &sigsegv_watcher, sigsegv_cb, NULL, SIGSEGV);
-
 	/* Stopping init is a bit tricky. */
 	uev_signal_init(ctx, &sigstop_watcher, sigstop_cb, NULL, SIGSTOP);
 	uev_signal_init(ctx, &sigtstp_watcher, sigstop_cb, NULL, SIGTSTP);